A population-based case-control study of the relationships between various trace elements, as measured in toenails, and cancers of the larynx, esophagus and oral cavity is proposed. The specific aims are: (a) to determine whether a deficiency of selenium and, in particular, whether the ratios of selenium to arsenic and of selenium to cadmium are related to the development of laryngeal, esophageal and oral cancers; (b) to ascertain whether extreme levels of iron are related to the development of cancer of the pharynx, esophagus and larynx; (c) to investigate the relationship between esophageal cancer and a deficiency of molybdenum; and (d) to examine whether exposure to excess levels of nickel and chromium are related to laryngeal cancer and to determine whether the relationship between nickel and laryngeal cancer, if any, is modified by the amount of manganese present. The investigation will be conducted in King, Pierce and Snohomish counties in Washington State. The proposed study is an adjunct to an ongoing epidemiologic study of laryngeal, esophageal and oral cancers funded by NIH. The same case and control groups will be used for the proposed study of trace elements and cancer as in the ongoing study. Cases are obtained through the population-based SEER tumor registry in northwestern Washington State. Controls are selected using a random digit dialing procedure and are frequency matched by sex and age group to the oral cancer cases. Each case and randomly-selected population control will be asked to donate a clipping from each of his/her big toenails for trace element analysis. The toenails collected will measure exposure from one to two years prior to clipping, depending upon the age and sex of the subject. Thus, the levels of trace elements obtained will measure exposure prior to the diagnosis of cancer for the case group. Instrumental neutron activation analysis will be used for trace element analysis.